Success or otherwise in your hobby foundry will depend to a large degree on your skills & potential to create uncomplicated patterns, i.e.
Patterns that are easy to mould, lift or cut off from the sand
mould after a diplomatic rap.
A pattern that has incorrect draft on vertical surfaces, badly complete angle fillets, or a pattern that has not been complete to an ultra plane discontinue will be difficult to work with.
Hobby
Pattern production is an art in itself, pattern making
apprenticeships take nearby three or four years to complete, before you are given your “Trade Ticket”.
The midpoint hobby foundry employee most likely won’t have the time, or the patience to get involved with the art of pattern production to that extent.
But the basic skills are worth the attempt to learn, because
without them you wont get far with your hobby foundrywork, unless you Pay to have all of your patterns made for you, but that would take all of the fun out of it, and also cost you a sizeable number of money.
Construction costs of pro pattern production can vary from a few hundred dollars for uncomplicated patterns, up to several thousand dollars for involved pattern designs.
I happen to a know a pattern maker who designs and builds patterns & core boxes to make alloy & cast iron cylinder heads, it is not unusual for pattern & core costs to be nearby ,000.00 Au before you even think about melting & pouring any metal.
If you are a inheritance of the old tech school ideas of the sixties
& seventies, there is a good opportunity that you still remember how to skilfully use woodwork hand tools.
Some of the finest foundry patterns were made using basic hand tools. More than likely you still have a chisel set tucked away in a drawer, or a spoke shave, wood plane & handsaw, plus
a host of other tools that could be used to make exquisite patterns in the home hobby shop.
And if they happen to be a bit rusty, then get them out again and bring them back to life, re-grind the cutting edges and hone
them with an oil stone.
Remember what your trade educator all the time told you; “sharp tools
give the best results.”
Do the same with the wood plane and any other tools, such as a small set of carving chisels you could use to carve intricate shapes in wood.
You’ll need some good pattern timber or lumber as it’s called in the states… Doesn’t matter, it’s all wood isn’t it. There are many types of timber convenient for pattern making, but, you’ll probably be petite to what’s ready in your area or region.
Quality pattern timber is high-priced to buy, so ask for off cuts at the local timber merchant, which you may get for a requisite discount
You’ll be seeing for a soft timber that doesn’t splinter, has a right grain, is easy to work or carve, and finishes to an ultra plane finish.
One of the easiest timbers to use is jelutong, this timber comes from the Philippines, I don’t know whether it is from plantation timber, or old increase forests, but it is great to turn on a lathe, or shape and carve with sharp hand tools.
Some of the other pattern timbers in use are cherry wood, mahogany, maple, white pine, and many others.
Quite often a devotee pattern can be made from timber, and then a replica mould is made using Rtv 585 silicone, this is a quick recipe to remake replica output patterns.The replica patterns can then be mounted onto a match plate along with the runners & gates, this recipe will enable you to mould & cast many parts at the same time.
With a petite practise you will soon know sufficient to make inexpensive potential patterns that create good sand moulds.
There is one prominent pattern production tool that will make you wince when you purchase, but it is an prominent tool to have if you want to make exact patterns where shrinkage rates are concerned.
The tool is the “Pattern Makers Rule”, this is a ruler about 500mm (20″)long. Made by Rabone Of England. No B5. And the graduations are marked as: 1/30-1/40-1/60-1/80,
The graduations rehearse the number of shrinkage allowance for different types of metals. The pattern makers ruler provides a built in shrinkage percentage, which means you don’t have to fancy the final determination or size of your pattern, you plainly take your determination from your shrink rule, and replacement the determination to the pattern being made.
The ideas is quite clever in the way it’s all been calculated.
For a quick example, the 1/30 scale determination seems to give
the exact supervene with patterns used for cast aluminium items.
Machining allowance on specific parts of a given pattern may also need to be considered, generally your own judgement can be used to judge that.
Pattern production can be quite a challenge for the hobby foundry worker, but once you learn the basics and fabricate your skills, with a petite institution your patterns will get good and so will the whole casting quality.
If you intend on production lots of patterns, the speculation in a shrink rule is well worth the money.
And while you’re at it buy a good book on pattern making, it deserves a study all on it’s own, but it forms an integral part of foundry work, and because you’re the boss of your own workshop, you have to learn to wear the hat of the pattern maker & that of the sand moulder & founder.
Sounds like a whole lot of work doesn’t it, but you’ll soon learn what will work best for you. Spend the time to learn all you can, and you’ll be rewarded with encouraging results.
Col Croucher.
Basic Pattern making In The Hobby Foundry
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